Boron has a volumetric heat of combustion (i.e., energy density) more than three times that of the best practical hydrocarbon fuels, and is one of the few materials where both volumetric and gravimetric energy densities are well above those for hydrocarbons. For this reason, there has been research for decades aimed at using boron or boron-rich materials as a fuel or fuel additive in liquid or solid-fueled propulsion systems. Boron's potential as a fuel has not, to date, been realized, partly due to the difficulty in igniting and burning it efficiently. One problem is that boron is quite refractory (Tvap=2800K), thus combustion depends on heterogeneous reactions, which tend to be slow and diffusion limited. This limitation can be mitigated, at least in principle, by using nanoparticulate boron, leading to large surface-area-to-volume ratios, as suggested by a number of previous researchers. A limitation to this approach is that boron exposed to air forms a passivating native oxide layer that inhibits oxidation. Furthermore, as the particle size decreases, this oxide makes up an increasing fraction of the particle mass, and thus reduces the energy density.
There have been a number of previous reports of boron nanoparticle production using methods such as gas phase pyrolysis of diborane or solution-based synthesis routes that involve several steps. There also have been several approaches reported to coating boron particles with passivating overlayers, aimed at preventing air-oxidation, and thus enhancing ignition and combustion. Glycidyl azide polymer (GAP) has been used to coat boron particles. However it was shown in these studies that the GAP coating interacts with the boron through its native surface oxide layer; the boron particles used were already oxidized. Slurry fuels have been produced containing liquid hydrocarbon based fuels, boron and a fluoropolymer. In some cases they also included polyolefin amide alkeneamine surfactant in the slurry. In each case, the surfaces have an oxide layer that interacts with the surfactants.